Carburetor fuel-air proportioning mechanism

ABSTRACT

A GASEOUS FUEL-AIR PROPORTIONING MECHANISM FOR CARBURETORS COMPRISING A PAIR OF VALVES SPACED DOWNSTREAM AND UPSTREAM OR A FUEL DELIVERING POINT IN THE BORE OF A CARBURETOR WITH ONE BEING THE THROTTLE VALVE AND LOCATED IN PROXIMITY TO THE MANIFOLD OF THE ENGINE AND THE OTHER BEING AN AIR METERING VALVE OF LESSER DIAMETER THAN THE CARBURETOR BORE AND LOCATED UPSTREAM OF THE THROTTLE VALVE AND UPSTREAM OF THE FUEL INLET, SO THAT THERE IS A RELATIVELY CONSTANT PRESSURE DROP ACROSS THE AIR METERING VALVE AND THE FUEL METERING POINT. THE MECHANISM INCLUDES A FUEL METERING SYSTEM HAVING A FUEL VALVE WITH A CAM SHAPED EDGE OPERATED SEQUENTIALLY WITH THE AIR METERING VALVE TO REGULATE THE QUANITY OF FUEL INDUCTED INTO THE CARBURETOR BORE WITH THE FUEL METERING SYSTEM BEING CO-ORDINATED WITH THE THROTTLE   VALVE AND AIR METERING VALVE SO THAT THEY ARE OPERATED SEQUENTIALLY.

June 13, 1972 GARRETSQN ETAL 3,669,636

CARBURETOR FUEL-AIR PROPORTIONING IECHANISM Filed Oct. 20, 1969 3 Shuts-Shut 1 KEITH H. GARRETSON AND OWEN LGARRETSON INV T S ATTORNEY June 13, 1972 K. H. GARRETSON ETAL 3,669,636

cmsuamon FUEL-AIR raoroa'rronme MECHANISM FlLed Oct. 20, 1969 3 Shoots-Shut I KEITH H. GARRETSON AND OWEN L. GARRETSON INVENTOR ATTORNEY June 13, 1972 H. GARRETSQN ETAL 3,669,636

CARBURETOR FUEL-AIR PROPORTIONING IIECHANISM Filed 061'" 20, 1969 3 Sheets-Shut;

KEITH H GARRETSON AND OWEN L. GARRETSON INVENTOR (,ZA BY ATTORNEY United States Patent Office 3,669,636 Patented June 13, 1972 US. Cl. 48-180 P 13 Claims ABSTRACT OF THE DISCLOSURE A gaseous fuel-air proportioning mechanism for carburetors comprising a pair of valves spaced downstream and upstream of a fuel delivering point in the bore of a carburetor with one being the throttle valve and located in proximity to the manifold of the engine and the other being an air metering valve of lesser diameter than the carburetor bore and located upstream of the throttle valve and upstream of the fuel inlet, so that there is a relatively constant pressure drop across the air metering valve and the fuel metering point. The mechanism includes a fuel metering system having a fuel valve with a cam shaped edge operated sequentially with the air metering valve to regulate the quantity of fuel inducted into the carburetor bore with the fuel metering system being co-ordinated with the throttle valve and air metering valve so that they are operated sequentially.

This invention relates to improvements in fuel-air proportioning mechanisms for gaseous fuel carburetor. In particular it comprises a mechanism which maintains a relatively constant pressure differential across the air metering valve and across the fuel induction point in the carburetor bore and regulates the fuel intake in accordance with the air fiow through the bore of the carburetor through a linkage between the fuel metering valve and the air metering valve.

There are in the prior art other carburetors which make use of the principle of varying air flow and fuel flow simultaneously in the carburetor. These devices use various types of valving arrangements for delivering fuel into the carburetor air stream and for controlling the fuel-air mixture. The prior art devices are complicated, however, and delicate and do not achieve sufficient accuracy in the fuel mixture inducted into the engine.

In some of the prior art devices the fuel delivery point is subjected directly to manifold pressure. This exposes the fuel inlet to great suction and to great fluctuations of suction and requires extreme accuracy in machining the valving system for the fuel inlet. In addition minor wear on the valving system results in great inefficiency in the carburetor itself. Therefore it is desirable to establish control over the suction at the fuel inlet point to the bore of the carburetor in order to make it less sensitive to imperfections, to wear and tear and to manufacturing tolerances. In addition with a controlled suction the wear rate on the fuel valving system is low and the manufacturing tolerances are not as high as with prior art devices. Moreover it is desirable to correlate the fuel delivery to the air flow so that the most desirable fuel-air mixture is delivered into the system for a particular throttle setting.

It is therefore an object of this invention to provide an improved carburetor which has a controlled pressure drop across the fuel metering system and eliminates direct exposure of the fuel delivery point to the manifold suction.

Another object of this invention is to correlate the fuel intake into the carburetor with the air flow and the throttle setting.

A further object of this invention is to provide a carburetor fuel-air proportioning system which is insensitive to wear and tear on the valve parts and does not require close tolerance in the manufacture of the valve parts.

Another object of this invention is to provide an improved carburetor fuel-air proportiouing mechanism which controls the pressure drop across the fuel-air metering systems and simultaneously controls the fuelair mixture into the carburetor.

Other and further objects of this invention will become obvious as the same is better understood by reference to the following specification and accompanying drawings wherein:

FIG. 1 is a top view of one embodiment this invention.

FIG. 2 is a cross-sectional view of the embodiment of the invention shown in FIG. 1 taken along lines 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view of the embodiment of this invention shown in FIG. 1 taken along lines 3-3 of FIG. 1.

FIG. 4 is an exploded view of the fuel metering system shown in FIG. 3.

FIG. 5 is a top view of a second embodiment of the invention designed for use with a governor.

FIG. 6 is a cross-sectional view of the embodiment shown in FIG. 5, taken along line 66 in FIG. 5.

FIG. 7 is a partial side view of the fuel metering valve mechanism shown in FIGS. 5 and 6.

The two embodiments of this invention shown in FIGS. 1-4 and 5-7 respectively are merely examples of the present invention. The first embodiment is designed for use with a gaseous fuel carburetor with the air-fuel metering system being connected directly to the throttle through a gear arrangement, while the second embodiment incorporates a diaphragm system or governor to operate the air metering system. These two examples are not intended to limit the scope of the invention which may be incorporated into many gaseous fuel carburetors.

In the two embodiments of the invention shown, like numerals refer to like parts. Thus carburetor 1|] consists of four basic parts; a fuel metering mechanism 11, a carburetor bore 13, a throttle valve 18 and an air metering valve 19.

Fuel metering mechanism 11 is housed Within housing 17 to form a chamber and includes a fuel metering valve 14 with a cam shaped leading edge controlling the size of fuel outlet 15 into fuel passage 16 into carburetor bore 13. The configuration of fuel metering valve 14 and the hole into fuel passage 16 may be varied as a matter of design. For example valve 14 may have a straight side with an odd shaped hole, or the two may be of some other desired shape, the important point being that valve 14 is operated sequentially with the throttle. Fuel valve 14 is rotatably secured over outlet 15 and positioned so that its leading edge moves across outlet 15 as the valve 14 is rotated so as to control the size of outlet 15 and thus the amount of fuel it will pass into fuel passage 16. Fuel passage 16 opens directly into the bore 13 of carburetor .10 so that fuel may be inducted from fuel metering mechanism 11 through outlet 15 into passage 16 and thence into the carburetor bore 13. The induction force and the suction to which passage 16 is exposed is controlled by the valving arrangement in the carburetor bore to be hereinafter described, while the amount of fuel passed into passage 16 is controlled by fuel valve 14 as previously described.

In the embodiment of the invention shown in FIGS. l-4, the operation of fuel metering valve 14 is controlled by carburetor throttle 21. As shown in FIGS. 2, 3 and 4, fuel valve 14 is operably connected to throttle valve 18 through a gear train. First gear 22 is connected to throttle 21 by throttle shaft 30 which is rotatable in bearing 31 and rotates with rotation of throttle 21 which also controls throttle valve 18. First gear 22 engages second gear 23 which is fixedly connected to fuel valve 14, both of which are connected to second shaft 32 which is rotatably supported in bearing 33. Air metering valve 19 is fixedly connected to second shaft 32 to rotate in carburetor bore 13. Its external configuration and diameter may be the same as the internal diameter of carburetor bore 13 with the exception of flat edges to be hereinafter described. Alternatively, air metering valve 19 may be of slightly lesser diameter than carburetor 13 to allow passage of air around its edges when valve 19 is closed.

Thus, movement of throttle 21 causes sequential rotation of throttle valve 18, first gear 22, second gear 23, fuel valve 14 and air metering valve 19, causing a sequential adjustment of all the working parts of the valving system. The relative degree of rotation between the members is determined by the initial setting of the valves, the shape of fuel valve 14, and the ratio between first gear 22 and second gear 23, which are a matter of design parameters for individual carburetors.

Sequential movement of throttle 21 and its attached valve 18, fuel metering valve 14 and air metering valve 20 regulates both the amount of fuel delivered into the carburetor bore and the pressure dilferential across air metering valve 19 and across the fuel induction point in carburetor bore 13. Thus as the pressure differential tends to increase with opening of throttle valve 18 and exposure of the carburetor bore to increased manifold suction, the sequential opening of air metering valve 19 reduces restriction to air flow through carburetor bore 13 tending to maintain the pressure differential constant across the inlet to air metering valve 19 and the fuel induction point. At the same time fuel metering valve 14 admits more fuel into carburetor bore 13 so that the fuel-air mixture remains relatively constant. Fuel metering valve 14 and air metering valve 19 could be adjusted to vary the fuelair ratio if desired. Flat sides 20 are provided on air metering valve 19 to allow passage of a minimum amount of air through air metering valve 19 when the valve is perpendicular to the longitudinal axis of carburetor bore 13 or closed and throttle 21 is in an idle position. Alternatively the diameter of air metering valve 19 could be reduced to allow passage of air around its edges. The relative positions of throttle valve 18, fuel metering valve 14 and air metering valve 19 can be adjusted simply by adjusting the point of initial engagement of first and second gears 22 and 23 respectively or the gear ratios. Fuel metering valve 14 and first and second gears 22 and 23 can be secured against rotation on their respective shafts by any suitable means, such as set screws or machined surfaces.

In order to maintain a tight frictional engagement of fuel metering valve 14 against fuel outlet 15, a compression spring 24 is provided. One side of spring 24 is seated over second shaft 32 and engages second gear 23. When the housing 17 on fuel metering system 11 is closed, the second side of spring 24 engages the inside cover of the housing 17 so that spring 24 is compressed to bias fuel valve 14 into engagement with outlet 15 to compensate for frictional wear on the surface of valve 14 and insure a tight fit.

Housing 17 may be secured to the carburetor body by any suitable means such as by means of screws 25 which pass through the housing 17 and engage screw holes 26. The throat of carburetor bore 13 may also be secured to the carburetor body by any suitable means, such as by nut and bolt arrangements 27. Suitable gaskets must be provided to prevent leakage at the connection points. Idle adjustment screws 28 are provided in the customary manner and idle ports 29 are provided, opening from fuel reception chamber 11 into carburetor bore 13 for fuel passage when metering valve 14 is closed.

As can be seen from the foregoing description, the operation of throttle valve 18, air metering valve 19, and fuel metering valve 14 occur sequentially. The rotational position of air metering valve 19 and throttle valve 18 can be preadjusted so that there is a predetermined suction at the fuel inlet. The restriction of air metering valve 19 to the air flow in carburetor bore 13 and the positioning of throttle valve 19 in proximity to the manifold of the engine controls the air pressure drop through the carburetor. Thus although the total air flow through the carburetor throat varies according to the degree of opening of the valves, the pressure drop across the air metering valve 19 and across the fuel induction point is relatively constant and the fuel mixture is relatively constant with the variation of the throttle setting.

Referring now to the embodiment of the invention as shown in FIGS. 5-7 it will be seen that the various parts of the invention as described in FIGS. 1-4 are the same with the exception of the linkage between throttle valve 18 and fuel metering valve 14 which has been eliminated, and with the addition of a diaphragm type control over the operation of air metering valve 19 and fuel metering valve 14.

As shown in FIG. 6 the carburetor air metering system is provided with a governor 36 having a diaphragm 37 secured therein which is initially positioned and biased by a bias spring 38. An adjustment screw 39 engages one end of bias spring 38 with the other end being connected to diaphragm 37. The degree of insertion of adjustment screw 39 determines the force of spring 38 and thus the bias of diaphragm 37. An air intake 40 shown in FIG. 5 into carburetor bore 13 is provided in the usual manner to allow intake of air during operation of the carburetor. Bias spring 38 is connected to diaphragm 37 by means of an attachment member 41 such as a rivet, nut or brad, which also attaches one end of a hollow coupling joint 42 to diaphragm 37. One end of hollow coupling joint 42 opens above diaphragm 37 while the other end is connected to air metering valve 19, with a slot 43 being provided in air metering valve 19 to enable relative movement of air metering valve 19 and the attached hollow coupling joint 42. Fuel metering valve 14 is connected to shaft 32 to which air metering valve 19' is also connected to provide simultaneous movement of the two members. Hollow connecting member 42 is only an example of one method of transferring pressure through diaphragm 37. Other means could be used, including a separate transfer tube, placing one or more holes through diaphragm 37 or some other suitable means.

The function of the governor type mechanism as described above is similar to the mechanism described in the embodiment shown in FIGS. 1-4 except that governor 36 rather than throttle valve 18 controls the operation of air metering valve 19 and fuel metering valve 14. When the carburetor is inoperative, diaphragm 37 is biased downward by the action of bias spring 38 the force of which is controlled by adjustment screw 39 and air metering valve 19 is closed. As throttle valve 18 is opened to expose carburetor bore 13 to greater manifold suction, the suction pressure is conducted through hollow coupling joint 42 into the chamber above diaphragm 37 to create an upward suction on the diaphragm against the force of bias spring 38. As can be seen in FIG. 6 hollow coupling member 43 is connected eccentrically to air metering valve 19 through slot 43. The upward movement of diaphragm 37 is transmitted to air metering valve 19 through its coupling with hollow coupling member 42 to open air metering valve 19 and thus allow a greater flow of air through carburetor bore 13. At the same time fuel metering valve 14 allows more fuel to be inducted to carburetor bore 13. Thus as throttle valve 18 is opened tending to expose the fuel induction point to a greater suction from the manifold of the engine air metering valve 19 opens to allow greater air flow through carburetor bore 13 thus tending to maintain a constant pressure differential between the carburetor air intake and the fuel induction point and a greater quantity of fuel is inducted into carburetor bore 13. Similarily as throttle valve 18 is closed tending to reduce the suction at the fuel intake point, air metering valve 18 is also closed to restrict air flow, again tending to maintain a constant pressure differential and fuel flow is decreased.

As was described in the embodiment shown in FIGS. 1-4, air metering valve 19' may be provided with flat sides so that a minimum amount of air is allowed to pass when air metering valve 19 is closed or the carburetor is at idle speed. The relative positions of the valves involved are determined by the initial setting of the valves. The relative positions of air metering valve 19 and fuel metering valve 14 to throttle valve 18 are controlled by the flexibility of diaphragm 37, the force of bias spring 38 and the manifold suction.

Thus it is apparent that the two embodiments of this invention shown in FIGS. 14 ad -7 operate in substantially the same manner with modifications being made as required by the structure of the carburetor itself. The results achieved by both embodiments are the same in that a constant suction pressure at the fuel intake in the carburetor bore is maintained with the air flow through the carburetor bore and the fuel fiow into the carburetor bore being adjusted depending upon the throttle setting. Obviously many modifications of the present invention are possible in light of the above teachings. As heretofore stated the two embodiments are exemplary of the invention and it is not limited to the specific examples shown.

I What is claimed is:

1. In a fuel-air proportioning mechanism for gaseous fuel carburetors, the combination comprising:

a carburetor having a bore;

fuel metering means having an inlet passage into said carburetor bore for introducing gaseous fuel into the bore of the carburetor; throttle valve means adjustably positioned within the carburetor bore downstream from the point of fuel induction into the carburetor for varying the manifold suction to which the carburetor bore is exposed;

air metering means adjustably positioned within the carburetor bore upstream from the fuel metering means for varying the flow of air into the carburetor bore;

control means operably connecting said fuel metering means, and said air metering means and said throttle valve means for sequentially varying the fuel and air fiow into the carburetor bore with adjustment of the throttle valve means so that the suction on the fuel metering means is constant and the How of fuel and air through the carburetor bore is varied.

2. The invention as defined in claim 1, including:

said fuel metering means comprising a housing operably connected to a source of gaseous fuel, a fuel outlet for delivering fuel into the carburetor bore and a fuel valve means operably connected to said fuel outlet for regulating the amount of fuel released from said fuel reception chamber into said carburetor bore; and

connection means operably connecting said fuel metering means to said air metering means whereby the operation of the fuel valve in said fuel metering means is correlated with the operation of said air metering means so that movement of one causes a corresponding predetermined movement of the other. 3. The invention as defined in claim 2 wherein; said air metering means comprises a shaft rotatably supporting an air metering valve within the interiorof said carburetor bore, said air metering valve being adapted to regulate the flow of air into the carburetor bore and having means thereon for allowing a predetermined air flow through said carburetor bore when said air metering valve is closed.

4. The invention as defined in claim 3 wherein;

said connecting means for connecting said fuel valve to said air metering means is the shaft to which air metering valve is connected; and

said fuel valve is removably attached to said shaft so that rotation of said shaft causes simultaneous rotation of said air metering valve and said fuel valve.

5. The invention as defined in claim 4 above wherein;

said fuel outlet means comprises an aperture communicating with a passage leading from said housing into said carburetor bore;

means on said fuel valve for adjusting the size of the outlet to vary the fuel fiow therethrough.

6. The invention as defined in claim 5 including:

linkage means linking said connection means for said fuel valve and said air metering means to said throttle valve means whereby rotation of said throttle valve means causes sequential rotation of said fuel valve and said air metering valve.

7. The invention as defined in claim 6 wherein;

said throttle valve is rotatably secured within said carburetor bore on a shaft which is perpendicular to the longitudinal axis of said cylinder bore with its two ends extending outside of said carburetor; and

throttle means connected to one of said two ends of said shaft for controlling the opening of said throttle valve.

8. The invention as defined in claim 7 wherein;

said linkage means includes a first gear means secured to the other of the two ends of said shaft to which the throttle valve is connected and perpendicular to the longitudinal axis of said shaft and a second gear means fixedly attached to said fuel valve and rotatable therewith;

said first and said second gear means engaging each other when the fuel-air proportioning mechanism is in operating condition so that movement of one causes movement of the other.

9. The invention as defined in claim 3 including:

governor means operably connected to said air metering means for controlling the operation of said air metering means.

10. The invention as defined in claim 9 wherein;

said governor means comprises a diaphragm, a connecting member, a diaphragm biasing mechanism, a sealed chamber and pressure transfer means for transferring pressure from one side of said diaphragm to the other side;

said diaphragm being positioned above said air metering means;

said connecting member comprising an elongated rod having two ends with one end being attached to said air metering valve in said carburetor bore and the other connected to said diaphragm, so that movement of said diaphragm is transmitted through said connecting member to said air metering valve to cause corresponding movement thereof;

said sealed chamber is above said diaphragm so that the diaphragm is located between the carburetor bore and the sealed chamber, and variations in pressure in the carburetor bore are transmitted into the sealed chamber through said pressure transfer means into said sealed chamber to cause movement of said diaphragm corresponding to the pressure variation; and

said diaphragm biasing mechanism comprises a compression coil spring housed within said sealed chamber with one end being attached to said diaphragm and the other end being attached to an adjustment member for varying the compression force of said spring whereby the diaphragm is biased downwardly toward said carburetor bore.

11. The invention as defined in claim 5 including;

means for biasing said fuel valve into engagement with said aperture. 12. In an improved carburetor fuel air proportioning mechanism the combination comprising:

a fuel metering mechanism, a carburetor having a bore, a throttle valve and an air metering valve; said fuel metering mechanism being attached to said carburetor and being formed into a chamber with a fuel passage leading from said chamber into said carburetor bore and a fuel valve controlling passage of fuel from said chamber into said carburetor bore;

said throttle valve being movably positioned within said carburetor bore downstream from the fuel passage into said carburetor bore to thereby control the degree of exposure of said carburetor bore to the manifold intake of an engine to which said carburetor is attached;

an air metering valve rotatably positioned within said carburetor bore upstream from the fuel passage into said carburetor bore to thereby control the amount of air flow through said carburetor bore;

fuel air control means operably connecting said throttle valve, said fuel metering valve and said air metering valve whereby movement of said throttle valve causes a predetermined sequential movement of said fuel valve and said air metering valve to thereby adjust the flow of air and fuel through said carburetor bore in a predetermined manner.

13. The invention as defined in claim 12 including a first gear fixedly attached to said throttle valve and a second gear fixedly attached to the fuel valve, said first gear operably engaging said second gear so that movement of one causes corresponding movement of the other;

a third gear fixedly attached to said air metering means and engaging said second gear on said fuel valve whereby movement of any one of the three gears causes corresponding movement of the other two MORRIS O. WELK, Primary Examiner R. E. SERWIN, Assistant Examiner U.S. Cl. X.R.

48--l80 R; l23-ll9 DB; 261-50 R 

